Major road and rail construction schemes typically several years to complete. Use this key to denote active construction sites (for projects being planned, where there is little or no evidence for them on the ground, use proposed=* instead).

Concerning tagging already existing features as being under construction (e.g. old, damaged roads getting rebuilt): As OSM data is often used offline (and therefore may be several months old), only tag construction sites (particularly roads and railroads) if they are planned to be closed for at least six to nine months. Don't use construction=* to tag short-term closures (e.g. a road closed over a weekend to replace a sewer pipe); consider using conditional restrictions instead.

A deprecated option is to set the tag construction=yes. While this allows you to tag just about any feature as being "under construction", it won't be supported by the map renderers and other data consumers, and is therefore not recommended. A lifecycle prefix is usually the preferable alternative for such features.

If you know the date at which a construction site is expected to be completed, you can tag it with opening_date=*. Additionally, you can use check_date=* to denote when you last checked/updated the values (this can be useful as large construction projects are often delayed).

For instance, to tag a residential road under construction, use highway=construction and construction=residential. To tag a tramway under construction, use railway=construction and construction=tram.

Highways

In addition to using highway=construction, you should also tag the type of highway being built by using construction=*. For instance, to mark a primary road under construction, tag it with highway=construction and construction=primary.

For minor road-works (where the road in question remains open), use construction=minor (and don't use highway=construction, but leave it at its default value).

Values

highway=construction with any of the following values for construction=* will render on the default Mapnik layer at zoom level 12 and above:

In all cases, the way will be rendered as a dashed version of the corresponding highway=* tag.

Railways

Similarly to highways above, tag the railway under construction with railway=construction and the type of railway being built with construction=*. The following values for construction=* will render on Osmarender at zoom levels 14 and above:

In all cases, the way will be rendered as a dashed version of the corresponding railway=* tag.

Notes

Since most construction sites are not accessible to the public, it might be tough to get detailed GPS tracks of roads which have not yet been built. In that case, it's usually sufficient to roughly trace the route, and increase the detail level once the road is open.

See Also

proposed=*, for features which are being planned, but for which construction has not yet started.